Apparatus for deionizing liquids with ion exchange resins

ABSTRACT

Apparatus and method for operating a primary bed ion exchange resin demineralizer and for regenerating and backwashing the resins thereof. A spider-type distributor assembly having integral flow control means is installed in the top head of a resin-containing exchange vessel, to permit resin bed volume to substantially occupy the entire vessel volume, limited only by the in-service swelling characteristics of the resin. An auxiliary vessel, termed the resin drop tank, is provided for receiving a portion of the resin from the exchange vessel to accomplish backwashing of such portion outside the exchange vessel and all or none of the remaining resin inside the exchange vessel before replacing and regenerating the resin.

FIELD OF THE INVENTION

This invention relates to demineralization of liquids and, moreparticularly, to water treatment by the use of ion exchange resins.

BACKGROUND OF THE INVENTION

Demineralizer systems for removing ionized particles from water for thepurpose of purification have been known in the prior art for aconsiderable period of time. In such systems, untreated water ispurified by flowing it through beds consisting of cation and anionexchange resins. Two types of resin beds may be employed, primary bedscontaining either a cation or an anion exchange resin, but not both, andmixed beds containing both cation and anion exchange resin beds mixedtogether. Frequently, systems will employ multiple vessels or tankscontaining primary resin beds for performing initial demineralization,followed by a final stage of treatment in a vessel containing a mixedresin bed. The treatment capacity of such a train of demineralizerstages is thus principally limited by the estimated exchange capacity ofthe primary bed tanks, i.e. fluid volume treated per interval betweenresin regeneration, for a given influent water composition.

Characteristically, exchange capacity is defined on the basis of userneeds and then translated into the volume of cation and anion resinsrequired to provide the desired performance. Once the required resinvolume has been established, it is then possible to determine the sizesof the vessels required for containing the resin beds. According toconventional practice, ion exchangers consist of a plurality of vesselsin which the actual ion exchange process takes place, together withassociated control apparatus, piping and valving. Each vessel comprisesa vertical or upright tank housing a bed of exchange resin materialtherein. One or more distributors are provided within the upper regionof such a vessel and a collector system is provided in the bottom regionthereof. Since the resin expands during backwashing, and as it goes fromregenerated to exhausted form, a significant portion of the volumewithin the vessel is empty of resin during the in-service, ion-exchangeprocedure, to allow sufficient "rise space" to accommodate suchexpansion.

According to the conventional system set out above, both the service andregeneration fluid flows are in a downward direction. That is, fluid isintroduced into the top of the exchange vessel and flows downwardtherethrough. The resin or the bed may either expand during regenerationand shrink during exhaustion, or vice versa, depending on thecharacteristics of the particular resin selected. When multipledistributors are used, the regenerant is introduced through one, withthe other being employed for the service and backwash flows.

Another prior art system is characterized by so-called counterflow or"counter-current" operation. According to this principle, the influentliquid to be treated flows downward through the resin bed andregeneration is accomplished by an upward flow, or vice versa.

The flow of the influent liquid to be treated through the resin bed,gives rise to ion exchange zones which are displaced accordingly throughthe exchange material as the resin bed becomes progressively exhausted.In other words, ions which are most easily trapped by the resin areremoved from the fluid in the first portions of the bed. Less easilycaptured ions which are more loosely bound are displaced from the resinby the more easily captured, tightly bound ions and do not find exchangesites until they reach positions in the latter portions of the bed. Whena sufficient number of exchange sites on the resin have been exhaustedby trapped ions, efficient purification is no longer possible. Liquidwill pass through the bed untreated. At this point, it is necessary toterminate processing and to backwash the resin bed to remove suspendedmatter. Regeneration and rinsing of the resin are then accomplished bybringing suitable chemical solutions into contact with the resin, tochemically strip the trapped materials from the resin beads, and thenrinsing out the excess regenerant and the impurities.

Regardless of which of the foregoing operational schemes is employed, itis necessary to allow sufficient volume in the vessel to accommodatechemical swelling of the resin bed. In prior art systems with resinvolumes and vessel size selected for specific site requirements, suchchemical swelling is accommodated in various ways. For example, in theconventional downflow service vessel wherein downflow regeneration ispracticed, an allowance is made for chemical swelling by providingsufficient volume within the vessel to permit upward backwashing of theresin, within the vessel, prior to regeneration. Since backwashingrequires that the packed resin beads be agitated apart to free trappedmaterials and expose the surfaces of the beads in preparation forregeneration, the volume expansion of the bed associated withbackwashing is generally several times that associated with theaforementioned chemical swelling. In some types of counterflow schemes,involving upflow regeneration in a downflow service vessel, an allowancefor backwash expansion will also be sufficient to provide for chemicalswelling. However, in both of these cases, unless the service vessel hasbeen deliberately oversized, additional resin cannot be loaded into thevessel without eliminating needed rise space. And, indeed, suchoversizing would be economically inefficient, in any event.

In a contrasting type of counterflow system, the resin bed is compressedupwardly against a retaining collector either during service orregeneration, and backwashing in the service vessel is not practical perse. Therefore, a certain amount of vessel volume must be provided asrise space to accommodate resin swelling. Should additional rise spacebe provided to permit expansion during backwash, the resin-retainingupward flow collector would not permit the passage of dirt from thevessel. Therefore, this type of counterflow application requires theperiodic removal of all of the resin from the service vessel, to cleanseit of foreign material. With this design, overall vessel height isrestricted to only that amount needed to contain the resin volume, toaccommodate swelling, and to ensure hydraulic efficiency in either theupflow service or regeneration steps. To load additional resin in thevessel in excess of the amount needed for the specific requirements atthe time of installation would, therefore, require that the servicevessel be made larger than needed, which would be economically wastefuland detrimental to hydraulic efficiency.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for operating primary cationand anion exchange vessels with substantially greater quantities ofresin than permitted by prior art designs and methods. This permits asubstantial increase in exchange capacity as compared with the priorart, for vessels of like size. As more fully explained below, thepresent invention permits resin bed depth to be increased until almostthe entire vessel is filled with resin, without regard to rise spacerequirements and without restricting the backwashing operation, therebymaking possible a 75-100 percent increase in exchange capacity withoutthe need for additional exchange vessels. In addition to being suitablefor installation as a complete system per se, the present invention isalso uniquely well adapted to enable prior art installations to bemodified according to the teachings herein, to increase their exchangecapacity at minimal cost. Consequently, this invention provides a way ofincreasing exchange capacity of existing demineralizer systems withoutrequiring the installation of entire additional trains of exchangevessels.

To achieve these results, the present invention incorporates a special,remotely-controllable hub lateral assembly comprising a spiderdistributor which is installed in the top head of an ion exchangevessel, to permit and control fluid flow into and out of the vessel. Thespider distributor is provided with a hub containing a central fluidpassage and at least two sets of laterally disposed fluid conduitsthrough which fluid may flow between the vessel interior and the centralfluid passage of the hub. Internal flow control means are providedwithin the hub, responsive to an external control, for apportioning theflow between the sets of lateral conduits, to achieve efficienthydraulic operation.

The central fluid passage of the distributor hub is connected outsidethe exchange vessel to appropriate piping for supplying and removingboth water and regenerating chemicals, and inside the vessel to achamber in the hub which is in fluid communication with a first set oflateral conduits. The internal flow control means of the distributor hubassembly comprises a diaphragm valve which is used to selectively openor close a passage from the chamber to a second set of lateral conduits.The state of the diaphragm may be hydraulically or pneumaticallycontrolled, in response to pressure applied thereto through a diaphragmcontrol device mounted externally to the vessel. During regenerantintroduction and displacement, the diaphragm is automatically closed, sothat there is no flow through the second set of lateral conduits; andduring service, rise and backwash operations, the diaphragm is opened,permitting flow through both the first and second sets of lateralconduits.

All of the lateral conduit elements are provided with numerous openingsor ports therein to permit fluids to flow between the vessel interiorand the inside bore of each of the conduits. The openings of the firstset of lateral conduits, however, are screened by a closely spaced wirewrapping or mesh, to prevent resin beads from passing therethrough.Otherwise, during those stages of operation in which water or regenerantflows out of the vessel through the distributor, resin beads might alsoflow out of the vessel and be lost. The principal consideration insizing the holes of the lateral conduits is the providing of properhydraulic conditions. Thus, the holes on the first (i.e., upper) set oflateral conduits are sized according to the hydraulic flow requiredduring regenerant introduction and displacement, and the holes on thesecond (i.e., lower) set of lateral conduits are then sized according toservice flow requirements.

As stated above, according to the present invention, the depth of theresin bed in a primary bed exchange vessel is increased until almost theentire vessel is filled with resin. Sufficient void space is allowed,however, to permit expansion and contraction of the resin duringregeneration and in-service exhaustion. Typically, this expansion is onthe order of 12 to 22 percent of initial bed volume. In a cylindricalvessel, this implies a corresponding 12 to 22 percent increase in beddepth. To accommodate this expansion, about 15 to 25 percent of thevessel volume must initially be free "void" space unoccupied by resin orequipment, so that the resin expansion can take place. Thus, accordingto the present invention, the resin bed initially occupies about 80% ofthe vessel volume.

However, as noted above, the resin bed volume must expand to a greaterextent during the backwashing operation to permit the removal andwashing out of physically trapped materials from the resin bed.Typically, a 75 to 100 percent expansion is needed for adequatebackwashing. Since the resin bed initially occupies about 80 percent ofthe exchange vessel volume, prior to backwashing a predetermined portionof the resin bed must be removed from the exchange vessel, to allow forsuch expansion of the remaining portion of the bed. The predeterminedquantity of resin is therefore removed from the exchange vessel via aresin transfer nozzle and appropriate piping and valving, andtransferred to an accessory tank. This permits the level of the resinbed remaining in the exchange vessel to drop (and then expand duringbackwashing). For this reason, the accessory tank is referred to as a"resin drop tank", or RDT, for short and the exchange vessel is called a"dropped bed resin tank", or DBRT. The very act of transferring servesto backwash the displaced resin to some extent. However, the transferflow is continued if necessary to completely backwash the displacedportion of the resin bed. After the resin which remains in the exchangevessel is backwashed and the resin from the RDT is returned to theexchange vessel, the backwashed resin is regenerated and returned toservice.

Since regeneration is confined to the exchange vessel, no chemicalactivity takes place in the RDT. Thus, the RDT may be extremely simplein design and inexpensive in construction, employing easy-to-usematerials, such as fiberglass. Moreover, since the RDT is used onlyduring the backwashing and regeneration operations, if several exchangevessels are operated on different, staggered schedules such that no twoof them require backwashing and regeneration at the same time, thispermits a single RDT to be time-shared (i.e., multiplexed) between theseseveral exchange vessels. Also, there is no need to maintain stricttemperature control of the RDT environment; this represents additionalcost savings over the prior art. Finally, it should be realized that theRDT may even be located remotely or exterior to the building or areaoccupied by the existing demineralizing train(s), thus permitting systemcapacity to be increased easily even where space is limited, withoutincurring the added expense associated with building alteration or newconstruction.

By contrast with the benign environment of the RDT, chemical activitydoes take place within the demineralizer system's anion and cationexchange vessels and they are, therefore, of special construction.Normally, these vessels are lined with rubber or plastic linings toprotect the metal walls of the vessels against the corrosive effects ofthe acidic/caustic conditions which exist therein. Therefore, both inadapting the present invention to existing systems, and in constructingnew demineralization systems, it is necessary that the resin transfernozzle installed on the side of the exchange vessels not destroy theintegrity of this lining. A nozzle has been designed which is suitablefor installation in both new and existing systems. In adapting thepresent invention to existing demineralizer trains, it is particularlypertinent that this resin transfer nozzle, described in detail below,permits existing exchange vessels to be modified without violating theapplicable ASME code requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present invention are more fullydescribed below in the detailed description of the preferred embodiment,presented for purposes of illustration and not by way of limitation, andin the accompanying drawing in which:

FIG. 1 is a schematic diagram of a primary bed ion exchange vesselassociated with a resin drop tank according to the present invention;

FIG. 2 is a regeneration sequence chart showing valve conditions for thepreferred embodiment of the present invention and wherein open valvesare indicated by the letter "X";

FIG. 3 is a partially sectioned side view of a hub lateral assemblyintended according to the present invention;

FIG. 4 is an exploded, pictorial view of an optical portion of the hubassembly of FIG. 3; and

FIG. 5 is a side sectional view of a resin transfer nozzle according tothe present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In general, the de-ionization of liquids with ion exchange resins isaccomplished in the above-described prior art systems by an operationalsequence involving three distinct operations. First, the exchange vesselis placed in service until the resin becomes exhausted. Next, the resinis backwashed to remove trapped materials and to loosen the resin beads.This exposes the surface of the resin beads and prepares the resin forthe next operation, regeneration. The regeneration operation involvesthe introduction of an acid solution (in the case of cation resins) or acaustic solution (in the case of anion resins), to chemically strip theions which have been trapped by the resins. A rinsing operation is alsoassociated with regeneration, to remove the chemical solutions("regenerants") used to release the captured ions. Generally, atwo-stage rinse is employed. A first, slow rinse is used to displace theregenerant and to simultaneously provide a controlled contact timebetween the regenerant and the resin beads, at the desired solutionconcentration. Thereafter, water is introduced for a fast rinse toremove any remaining regenerant. The conductivity of the fluid as itleaves the exchange vessel is monitored and rinsing is terminated inresponse to such monitoring when conductivity reaches a predetermined,desired level. Thereafter, the vessel is returned to service and theoperational sequence repeated.

Referring now to FIG. 1, there is shown there in diagrammatic form anexchange vessel and an associated resin drop tank, with the requiredvalving and piping. The operational sequence for this system isqualitatively the same as that just previously discussed. However, inorder to explain the operation of the invention, it is preferable tobreak down the sequence into 12 principal steps. Three steps arecharacterized by the condition of the control valves and the resultingflows. To summarize the positions of the valves shown in FIG. 1, inassociation with these various steps, a regeneration sequence chart isprovided in FIG. 2. The diagram of FIG. 1 and the chart of FIG. 2 arejointly explained below. A brief digression will first be made, however,to explain the structure and functioning of the spider distributor ofthe hub lateral assembly shown in FIG. 3, so as to permit referencethereto in the subsequent description of the operation of the systemshown in FIG. 1.

As illustrated in FIG. 3, spider distributor 20 comprises an assemblywhich is located partially interior to the exchange vessel and partiallyexterior thereto. The exchange vessel 10 (see FIG. 1) is generallydefined by a wall 50 with an opening in the top thereof. Welded into thetop opening of the vessel is a metal collar 52, referred to as a "tankpad". The purpose of the tank pad is simply to serve as a convenientstructure upon which to mount the distributor. A rubber coating orlining 54 protects the interior of the vessel wall 50 and extends overthe bottom surface of the tank pad, up the central opening therein andout over the top surface of the tank pad. Holes are drilled and tappedinto the top and bottom of the tank pad for receiving mounting bolts 56and 58. The portion of the distributor assembly 20 mounted exterior tothe vessel comprises a pipe section 62 having an upper flange 69 and alower flange 64. The lower flange is fastened to the top of the tank pad52 by bolts 56. Pipe section 62 opens sideways into a third flange 68.This flange provides an attachment point for the valve nest and pipingthrough which liquid enters and exits at the top of the vessel. Upperflange 69 of pipe section 62 is closed by a reducing flange 70 having apacking bushing 72 threaded therein. Packing bushing 72 provides afluid-tight seal around a control tube 74 which is of substantiallysimilar diameter than the inside diameter of pipe section 62. On theother side of the packing bushing, one end of the control tube isconnected to a first port of a three-way solenoid valve 76. A secondport of the solenoid valve 76 is open to the atmosphere or a drain, asappropriate, to provide a vent VC. The third port of solenoid valve 76is connected to a hydraulic or pneumatic pressure supply, not shown, viapressure supply conduit P. On the inner side of the packing bushing, thecontrol tube is disposed within the interior, central passages of pipesection 62, tank pad 52 and pipe section 78, terminating at a second endthereof interior to the hub 80 of the spider distributor.

Hub 80 comprises, in general, an upper chamber 86 associated with afirst or upper set of lateral conduits 88 and being in fluidcommunication with central passage 18 via an opening in the chamberconnecting it with pipe section 78, a lower chamber 90 associated with asecond or lower set of lateral conduits 92 and a remotely actuable valveassembly for alternately closing off the upper and lower chambers fromeach other or permitting them to communicate with each other, asdesired. The upper set of lateral conduits is wrapped with a wire screenor mesh, as explained elsewhere herein. Hub 80 is fixed to tank pad 52by pipe section 78. The latter is secured to the tank pad by bolts 58through an upper flange 82 and to the top of the hub by bolts 59 passingthrough a lower flange 84 and received in the wall of the hub.

In general, the vessels of the type used for demineralizing fluids bymeans of ion exchange resins are cylindrical in shape, capped at theupper end by a curved head. To maximize the tank volume available forthe resin bed, pipe section 78 is made very short and the upper set oflateral conduits is made shorter than the lower set of lateral conduits.This permits at least the upper set of conduits to be disposed in thehead of the exchange vessel, above the straight part of the tank.

The valve structure associated with chambers 86 and 90 more particularlycomprises a movable diaphragm 94 for opening or closing the passagebetween the two chambers. This passage is provided by an upwardlyextending and centrally disposed wall portion 96 with an opening,sealable by the diaphragm, at the upper end thereof. Within the upperchamber is disposed a diaphragm stop member 98, resembling an invertedcup. The upper end of diaphragm stop member 98 opens into and receivesthe lower end of control tube 74. Diaphragm stop member 98 is suspendedabove the open end of lower chamber wall 96, spaced apart therefrom, bya diaphragm support wall 100. The diaphragm support wall encloses theupwardly extending wall portion 96, contains several ports or openings101 therein, and has a bottom flange 102 which is secured against theupper, outer wall of the lower chamber. Diaphragm 94 is secured againstthe under side of the rim of the diaphragm stop member 98, outside thecup-shaped portion thereof. When solenoid valve 76 is in the first ofits two states, responsive to a control signal provided thereby by acontrol system, not shown, the first port of the solenoid valve isconnected to the third port thereof. Thus, positive pressure isintroduced from pressure conduit P via control tube 74, to forcediaphragm 94 downward to engage the upper opening of lower chamber wall96, providing a seal thereagainst and thereby closing off lower chamber90 from upper chamber 86 and preventing flow therebetween. Of course,this has the additional effect of closing off lower chamber 90 fromcentral passage 18 and, consequently, from the piping connected toflange 68. When the solenoid valve is switched to the second state, thefirst valve port is connected to the second valve port. Correspondingly,control tube 74 is connected to vent VC. In this state, upward pressureagainst diaphram member 94 is not resisted by a downward pressure on thediaphragm. Rather, as a result of the venting connection just described,the presence of upward hydraulic pressure in the lower chamber willcause the diaphragm to move upward, releasing the seal on lower chamberwall 96, until it is in contact with and retained by the diaphragm stopmember 98. With the diaphragm in this position, the upper and lowerchambers are in fluid communication via the open end of wall 96 andports 101 in the diaphragm support wall.

A diaphragm suitable for the described functioning comprises a shapedand molded piece of flexible, water impermeable material which isresistant to corrosion. Numerous plastics and other polymers are ideallysuited to this application, such as neoprene, viton and HYPALON (aregistered trademark of E. I. duPont de Nemours & Co.).

While the lateral conduits may be attached to the hub assembly by anyconvenient type of construction, in the specific example describedherein, the hub walls are shown as being provided with tapped holes forreceiving the lateral conduits, and the lateral conduits are shown ashaving threaded ends adapted to be received by the tapped holes of thehub wall. It should be appreciated that no additional support structureis required for the upper set of lateral conduits, at least, a situationnot generally true of prior art distributors.

Further describing the specific example illustrated in the drawings, weobserve that the lower chamber and upper chamber of the hub assembly areformed as separate components which are bolted together to form thecomposite hub. This approach has been followed both to facilitateconstruction and, at least in part, to permit the accommodation of anoptical means for controlling the flow through the ports 101 in thediaphragm support wall 100. This flow control is provided by including ameans for varying the effective aperture size of those ports. Referringto FIGS. 3 and 4, it will be seen that this result is accomplished byinserting a ring 104 between the outside of lower chamber wall 96 andthe inside of diaphragm support wall 100, closely adjacent to thediaphragm support wall. Ring 104, termed the diaphragm port ring, isprovided with holes 105 which match the holes 101 of the diaphragmsupport wall. By rotating the diaphragm port ring relative to thediaphragm support wall, the region of coincidence between the holes ineach of those elements will determine the effective apperture size ofthe openings presented to the flow of water therethrough. A lockingmechanism is provided to permit the diaphragm port ring to be rotated tothe desired effective aperture size and then locked in place. Thislocking mechanism, as illustrated, comprises an arcuate slot 106 in thediaphragm port ring 104 and a matching threaded screw hole 108 in thediaphragm support wall. A screw 110 passes through the slot in thediaphragm port ring and into the threaded hole of the diaphragm supportwall, so that when the screw is tightened the two elements are lockedtogether. The inclusion of the aperture control feature provides thecapability, during assembly or maintenance, of compensating thedeficiencies in fabrication and specific resin bed conditions, byadjusting flow rates accordingly. Also, it makes possible the use of asingle design for both anion and cation units, with adaptation to theparticular application being merely a matter of adjustment.

It should be understood that gaskets are provided where required, eventhough the same are not explicitly indicated in the drawings ordiscussed herein.

The hub may be either cast and then drilled and tapped or made fromappropriately formed sheet stock. A stainless steel alloy is preferablyfor all of the elements of spider distributor, except where the contraryhas been indicated, such as the diaphragm. The wire wrapping orscreening on the lateral conduits of the distributor should be made of asimilarly corrosion-resistant material.

The invention may now be understood by making reference to FIGS. 1 and 2in the accompanying textual description of a complete operating cycle.

The first step is that of servicing or treating the influent water toremove impurities. In this step, exchange vessel 10 is filled with itscomplete complement of resin; as explained above, resin bed volume cansubstantially fill the interior of the vessel, provided sufficient risespace is available to allow the resin bed to expand as waste materialsand ions are accumulated therein. The service step is accomplished withvalves AA and E open and all of the other valves closed. Influentservice water enters the system at inlet port 12 and thus flows throughpipe section 14, valve AA and pipe section 16 into the main conduit 18of the spider distributor 20. The flow then proceeds outward through oneor more sets of lateral conduits 22 which are in communication with themain conduit 18 of the spider distributor. The lateral conduits eachcomprise a tube containing a central longitudinal bore and a pluralityof ports or holes for permitting the exterior of the tube to communicatewith the bore. Water flows from the central passage into the bores ofthe lateral conduits, out through their ports and into the interior ofexchange vessel 10. The service flow then encounters and travels throughthe resin bed, proceeding downward through the exchange vessel andexiting through the nozzle 25 in the bottom thereof, into pipe section24. Finally, the treated water proceeds through connecting pipe 28 andvalve E to a service flow outlet port 26.

When it becomes necessary to rejuvenate the resin bed, the backwashing,regeneration and rinsing activities are commenced. These begin withoperational step no. 2, expanding the resin bed to loosen the packedbeads of resin. While this step is optional in nature, it is helpful andgenerally will be rather short in duration, such as about one-half toone minute. For this step (assuming the valves are initially asspecified for the prior step), valves AA and E are closed and thefollowing valves are opened: VA, BA, TA, TB and WB. The described valveconditions permit the service water flow to be used to begin to loosenthe resin beads preparatory to dropping the level of the bed within theexchange vessel and transferring part of the bed to the resin drop tank.Thus, with the valve conditions as listed, service water continues toenter inlet port 12 and pipe 14, but now flows through valve BA and theconnecting pipes 28 and 24 into the bottom of the exchange vessel atnozzle 25. As a result of the pressure thus applied, the bottom of thepacked resin bed begins to loosen. With valves AA, WA, G and BB closed,the service flow must exit from the exchange vessel via resin transfernozzle 29 and valve TA. Since the bed is partially loosened at thistime, the stream of water leaving the vessel through the resin transfernozzle 29 will sweep resin beads along with it, through resin transferpipe 32 and valve TB, into the open nozzle 34 at the bottom of the RDT40. This flow empties directly into the interior of the resin drop tankand does not pass through the underdrain screen 42. The service waterexits from resin drop tank 40 through RDT hub assembly 44, into pipe 45.It then flows through valve WB and pipe 47 to waste water outlet port46.

Having thus prepared the resin bed, the third operational step may beperformed: transferring a portion of the resin to the RDT, to drop thelevel of the resin bed in the exchange vessel. To carry out this step,valve BA is closed and valve AA is opened. As a result of this change,service water which enters inlet port 12 and pipe 14 now flows throughvalve AA and pipe 16 into the main conduit 18 of the spider distributor20. The flow then proceeds outward through one or more sets of lateralconduits 22 and into the interior of the exchange vessel 10. As theservice flow exits from the exchange vessel through valve TA, it carrieswith it resin beads which have been loosened from the bed in theprevious step. The service flow including such resin beads then proceedsthrough valve TB and directly into the bottom of the RDT through opennozzle 34, avoiding underdrain screen 42. The service flow leaves theRDT through drop tank hub 44, pipe 45 and valve WB into pipe 47 whichterminates at the waste water outlet port 46.

It should be noted that the resin which is transferred to the RDT isinherently backwashed, to a limited extent, in the course of thetransfer process.

When the desired amount of resin has been transferred to the RDT,permitting the level of the resin bed in the exchange vessel to drop theintended distance, the resin transfer step is terminated and abackflushing operation, step no. 4, is performed to clean the resintransfer pipe 32 and associated valves of resin. This is accomplished byclosing valves VA, AA, TB and WB and opening valves AB, RB and WA. Withthis system configuration, service water which enters inlet port 12 willflow through pipe 15, valve AB and the drop tank hub assembly 44 intothe RDT. To exit from the RDT, the service flow will pass through theportion of the resin bed which has been previously transferred into theRDT, through the underdrain screen 42, and out of the RDT via nozzle 35.From that nozzle, the water proceeds through valve RB, resin transferpipe 32, valve TA and resin transfer nozzle 29, into the exchangevessel.

Reiterating and restating briefly the explanation given above, when thesolenoid valve 76 is in the second state, the main conduit 18 of thespider distributor will be in fluid communication with both the first(i.e., upper) and second (i.e., lower) sets of lateral conduits 88 and92. However, when the solenoid valve is in the first state, diaphragm 94will close off the lower set of lateral conduits (92) from main conduit18, provided that a sufficient pressure is presented via conduit P.

For the first three operating steps discussed above, the solenoid valveis preferably in the second state. The solenoid valve is switched to thefirst state for the fourth operating step. Thus, the service flow whichenters the bottom of the exchange vessel through valve TA will exitthrough only the upper set of lateral conduits 88 of the spiderassembly, into central passage 18, pipe section 16, and valve WA,finally leaving the system via pipe 47 and waste water outlet port 46.

The next (and fifth) operating step to be undertaken is that ofbackwashing the RDT. This is accomplished by closing valves AB, TA andWA, and opening valves BA, BB, WB and VB. The solenoid valve may be ineither state. Service water which enters port 12 flows through pipe 14,valves BA and BB, resin transfer pipe 32, and valve RB into the bottomof the RDT, below the underdrain screen 42. The service flow, since itis under pressure, then proceeds upward through the RDT, backwashing theportion of the resin bed which has been transferred into the RDT.Finally, it exits via drop tank hub 44, pipe 45 to valve WB, thenthrough that valve and pipe 47 to waste water outlet port 46.

After the resin drop tank has been backwashed, the next (i.e., sixth)step is to backwash the resin in the exchange vessel. This is achievedby closing valves BB, RB, WB and VB, and opening valve WA. The solenoidvalve should be in the second state. With this arrangement, servicewater enters port 12 and flows through pipe 14, valve BA, pipes 28 and24 and then into the nozzle 25 at the bottom of the exchange vessel. Theservice flow next passes through the underdrain strainer 25A in thebottom of the exchange vessel and backwashes the portion of the resinbed which has remained therein. Egress for the service flow is providedby the spider distributor 20. Since it is intended in the backwashingoperation to remove foreign matter from the resin bed, it is necessarythat such foreign matter be able to enter the lateral conduits of thespider distributor, to be washed out of the exchange vessel. Thus, theholes in the unscreened (i.e., lower) set of lateral conduits 92 shouldbe sufficiently large to permit such waste matter to enter the conduitswith the height of the resin bed in the expanded state kept sufficientlybelow the position of the spider distributor to prevent carryover andloss of resin. From the spider distributor, the flow is outward frommain conduit 18, through pipe 16 and valve WA, to pipe 47 and wastewater outlet port 46.

Upon the conclusion of the backwashing operation, the resin which waspreviously transferred to the RDT must be returned to the exchangevessel. This involves a two step technique. First, it is desirable,though optional to raise the portion of the bed which has remained inthe exchange vessel, to prepare the exchange vessel to receive the resinfrom the RDT, step no. 7. Next, the resin from the RDT is fed back intothe bottom of the exchange vessel, below the lifted portion of the bed,step no. 8. To accomplish step no. 7, valves AB, TA, TB, and WA areopened. The solenoid valve may be in either state. The service flowwhich enters through port 12 will be split into two components. A firstcomponent of the service flow will pass through pipe 14, valve BA, pipes28 and 24, and nozzle 25, into the bottom of the exchange vessel. Thiswill create an upward flow in the exchange vessel, pushing upward on andraising the portion of the bed which had remained therein.Simultaneously, the other component of the service flow enters the RDTthrough pipe 15, valve AB, pipe 45 and drop tank hub 44. Since valve TBis open, the service water will flow through the RDT to carry the resinwhich had previously been transferred into the RDT out the open nozzle34 in the bottom thereof (bypassing the underdrain screen 42) and backinto the exchange vessel via valve TB, resin transfer pipe 32, valve TAand resin transfer nozzle 29. The two components of the service flowwill be recombined within the exchange vessel and will depart therefromvia the spider distributor, finally leaving the system through pipe 16,valve WA, pipe 47 and waste water outlet 46. The solenoid valve ispreferably in the first state for this step, so that the flow out of theexchange vessel is through the screened set of lateral conduits only, toprevent an undesirable loss of resin.

Once the bed is raised, valve BA is closed and valve RA is opened (stepno. 8) so that the entire service flow can be directed through the RDT,to remove all of the resin therefrom and replace it in the exchangevessel. If the solenoid valve was not placed in the first state in theimmediately preceding step, that must be done in this step, since it islikely that resin beads will otherwise be lost from the exchange vesseland dumped with the waste water.

After the resin has been replaced in the exchange vessel, it isdesirable to perform a combined flush (step no. 9) of the RDT andappropriate portions of the piping. For this purpose, valves BA, BB andRB are opened, and valves TB and RA are closed. This again splits theservice water inlet flow into two components. The first component of theservice water flow is directed via pipe 14 and valve BA into pipe 28; atthe juncture of pipes 28 and 24 and valve BB, this flow component isfurther split into two streams. One stream enters the exchange vesselthrough pipe section 24 and nozzle 25 in the very bottom of the exchangevessel. The other stream is directed through valve BB and enters theexchange vessel through valve TA and resin transfer nozzle 29. Thesecond component of the service flow simultaneously enters the RDTthrough pipe 15, valve AB, pipe 45 and drop tank hub 44. It then flowsdownward through the RDT and the underdrain screen or strainer 42, outthe RDT via nozzle 35 and valve RB, and into the exchange vessel vairesin transfer pipe 32, valve TA and resin transfer nozzle 29. Asexplained immediately above, the service water departs from the exchangevessel through the spider distributor and is then released from thesystem through pipe 16, valve WA, pipe 47 and waste water outlet port46.

The backwashing operation is now complete and the resin is prepared forregeneration. The next step (no. 10) is the introduction of regenerantsolution. This is accomplished by closing valves AB, BA, BB, RB, TA, andWA and opening valves RA and G. The solenoid valve is in the firststate. With this configuration, the regenerant supplied to regenerantintroduction port 13 flows therefrom through valve G, pipe 16 and spiderdistributor 20 into the exchange vessel. The regeneration solutiontravels down through the resin bed, freeing trapped ions from the resinand carries them out of the vessel through the nozzle 25 in the bottomthereof. The spent regenerant solution is then discharged through pipes24 and 28, valve RA, pipe 47 and waste water outlet port 46.

Once the regenerant has been introduced, it is necessary, as the next(i.e., eleventh) step, that it be displaced throughout the resin bed, toprovide the desired contact time at the intended solution strength. Thisis achieved by terminating the introduction of regenerant at port 13while continuing to introduce water at that point. Usually there is amixing valve (not shown) for controlling the dilution of the regenerantprior to its introduction at port 13. Thus, this step is normallyaccomplished by merely closing the mixing valve as to the regenerant,while continuing to run water in. None of the other valve statesdescribed above is changed in going from the tenth to the eleventhsteps.

Finally, valve G is closed and valve AA is opened (step no. 12) to rinsethe regenerant solution out of the exchange vessel and prepare the resinbed for being returned to service. The rinse is accomplished by simplypermitting the service water supplied at port 12 to flow through pipe12, valve AA, pipe 16 and the spider distributor, into the exchangevessel, then through the resin bed and out nozzle 25, pipes 24 and 28,valve RA, and pipe 47, to be dumped at waste water outlet 46. Aconductivity probe 120 monitors the conductivity of the fluid flowingout of the exchange vessel. As the regenerant is displaced from theresin bed by the rinse water, the conductivity of the water in pipe 24(or 28) will decrease. The conductivity measurement obtained via probe120 is monitored by an automatic control systen (not shown). The controlsystem terminates the rinsing operation and restores the system toservice when an acceptably low level of conductivity is detected.

It is to be noted that the RDT is completely disconnected from theexchange vessel during the in-service and regeneration operations, sincevalves AB, WB, RB and TB are closed, and the RDT is entirely empty ofresin. Thus, a single RDT may be associated with multiple exchangevessels, by an appropriate staggering of the operating sequences of theexchange vessels and a multiplexing (i.e., time-sharing) of the singleRDT between them.

From the foregoing description, it will be apparent that the systemtherein set forth has as a further advantageous property the need foronly a single connection to the exchange vessel distributor, forconnecting to a single distributor, to accomplish operations previouslyrequiring multiple distributors, each of which required a separateaccess connection. Moreover, the single connection can be made through asingle centrally located tank pad, rather than through at least oneconnection on the side of the vessel, as was customary in the prior art.In other words, both service flow and regenerant can be introduced tothe exchange vessel via a single connection thereto and a single hublateral assembly.

Further referring back to the above test, it was stated that resintransfer nozzle 29 must be of a design which does not destroy theintegrity of the interior lining of the exchange vessel. A specialdesign for a suitable nozzle is shown in FIG. 5. The nozzle thereillustrated comprises a hollow, threaded sleeve 152 having a centrallongitudinal bore 154 and a shoulder 156 of greater diameter than thethreaded sleeve portion. To install the nozzle in an exchange vessel ofa prior art design (for the purpose of upgrading or retro-fitting theassociated system according to the present invention), a simple processis employed. First, from the inside of the vessel, a small portion ofthe vessel lining 54 is cut out to define an opening therein. A hole isnext cut or drilled through the vessel wall 50 within the open region ofthe lining. This hole should be just large enough to receive thethreaded sleeve portion of the nozzle, and the open region of the liningshould be just slightly larger than the hole in the vessel wall. Amolded gasket 158 is then placed against the vessel lining, overlappingthe region cut away therefrom and extending inwardly up to the hole inthe vessel wall. This gasket should be of a material which is inert tothe regenerant solutions and is slightly compressible and flexible, suchas a molded rubber. The shape of the gasket should optionally conform tothe shape of the nozzle and the curvature of the vessel wall and have acentral hole for receiving the threaded sleeve of the nozzle.Preferably, the cut edges of the lining would be tapered, to enhancesealing against the gasket. To further assist in sealing, a cement maybe used between the vessel wall and the gasket. The nozzle is theninserted from the inside of the vessel wall. A threaded lock nut 160 isturned down tight over the threaded sleeve of the nozzle, against theoutside of the vessel, so that shoulder 156 is brought into closesealing contact with gasket 158 which is, in turn, brought into sealingcontact with the portion of the vessel wall 50 which was exposed whenthe lining material 54 was cut away.

While the surface of nozzle shoulder 156 which is brought into contactwith gasket 158 should be shaped to conform the curvature of the vesselwall, as indicated in the drawing, it may be very costly to manufacturea nozzle with a shoulder of such design. In that event, a less costlyalternative (not illustrated) may be to form shoulder 156 with a flatsurface and to insert a washer between shoulder 156 and gasket 158. Thewasher would have a flat surface for abutting shoulder 156 and aproperly curved surface for contacting the gasket. This washer could bemade of a hard plastic or other similar material, while the threadedsleeve element would be easily fabricated from stainless steel. Ifnecessary to prevent leakage, a thin gasket could also be employedbetween the washer and the shoulder surface.

The resin transfer nozzle can be installed at any desired altitude ofthe resin bed, depending upon the quantity of resin to be transferred tothe RDT. Likewise, a plurality of nozzles could be installed at aplurality of positions, to allow for varying the quantity of resin to betransferred. Moreover, to enhance the hydraulic efficiency of thetransfer operation or to permit multiple uses of the resin transfernozzle, an additional distributor could be connected to the transfernozzle interior to the vessel and disposed within the resin bed.

Also, it should be understood that valves VA and VB are used in aconventional manner, to vent the drop tank and exchange vessel to theatmosphere. Thus, while such valves are above described as being openonly for the specified operating steps, they will normally be monitoredby an operator and opened for brief periods of time, at any step in theoperation, to vent accumulated air from the vessels, to preventdegradation of resin bed conditions.

From the foregoing description, it should be apparent that the presentinvention teaches certain additional features and advantages. Forexample, the resin exchange nozzle may be located at any desiredelevation in the exchange vessel to permit removal of a correspondingpredetermined portion of the resin bed. Thus, if the frequency ofbackwashing is increased, the amount of resin which need be removed fromthe exchange vessel may be decreased and the resin exchange nozzle maybe placed higher on the exchange vessel. Also, the diaphragm supportwall 100 and the diaphragm port ring 104 comprise a pair of flow controlmembers which together comprise means for proportioning flow between thesets of laterally disposed conduits. Moreover, diaphragm support wall100, diaphragm stop member 98 and flange 102 on the lower end of thediaphragm support wall are integrally formed so that diaphragm stopmember 98 closes one end of the diaphragm support wall and provides achamber, together with the diaphragm, which chamber may be pressurizedby pressure received from a fluid pressure source through the controltube, to accomplish the closing of the diaphragm valve.

Certain conventions regarding the terminology used herein should also benoted. The references herein to a spider distributor relate to thedistributor which would be disposed in the upper portion of an ionexchange vessel. In general, there would be distributors in both theupper and lower portions of an ion exchange vessel; however, it has notbeen necessary for purposes of describing the present invention todiscuss a lower distributor member which would be connected, forexample, to the lower nozzle 25 at the bottom of the exchange vessel.

In general, typical vessels used in ion exchange demineralizer systemscomprise a shell of right, circular, cylindrical configuration, havingsloped head sections capping the top and bottom ends of the cylinder.The distributor of the present invention is intended for placement inthe top or bottom head of the exchange vessel, preferably as close tothe top of or bottom head wall, respectively, the vessel as possible.This is accomplished by employing laterally disposed conduits havingradii which are substantially less than the radius of the shell of theexchange vessel, so that they may be placed in the sloping portion ofthe top head of the exchange vessel. In the case of a distributormounted in a vessel's top head it is contemplated, though not required,that the first, upper set of laterally disposed conduits will thus havea smaller radial extent than the lower, second set of laterally disposedconduits. In effect, this distributor placement, depending upon use(i.e. downflow or upflow), forms either a concentrated hydraulic sourceor sink, or both, within the confines of the head volume. To furtherelaborate on the functioning of the distributor, it is noted that thefirst set of laterally disposed conduits generally serves to distributea portion of the service flow throughout the upper region of the tophead, to achieve complete fluid flow within all portions of the resinbed therein. The second set of laterally disposed conduits distributesthe remaining portion of the service flow both in the lower region ofthe top head and the upper portions of the vessel shell, to achievefluid flow within all portions of the resin bed therein. Thus, themultiple operation of both sets of laterally disposed conduits creates acompletely formed, full flowing hydraulic source or sink to achievefluid contact with all portions of the resin bed within the vessel headand all portions of the resin bed therebelow. Also, the multipleoperation of both sets of laterally disposed conduits provides a greaterthan normal portion of the service flow directed through the first setof laterally disposed conduits by the predetermined setting of thediaphragm port ring relative to the diaphragm support wall, this portionof the service flow being a greater amount than the design flow (i.e.regenerant flow) used to size the first set of laterally disposedconduits. The pressure drop caused by such setting of the diaphragm portring serves to supplement the pressure drop inherent in the design ofthe second set of laterally disposed conduits, to achieve effectivecontrol of the backwash flow, such backwash flow being a lesser amountthan the higher service water flow.

It is further to be understood that the above-described preferredembodiment is intended to be exemplary only, and not limiting. Forexample, with minor changes, that same apparatus may be used as acounter-current, upflow regeneration system rather than the downflowservice-downflow regeneration example shown. Additional modificationsand alterations will readily occur to those familiar with the art. Thusit is intended that the scope of the invention be limited only asdefined by the following claims and equivalents thereto.

What is claimed is:
 1. An ion exchange vessel assembly for primary,fixed-bed demineralizers, such assembly being operable fordemineralizing an influent fluid flow and comprising:an ion exchangevessel; a quantity of ion exchange resin disposed within the exchangevessel; distributor means for providing fluid communication between theinterior of the exchange vessel and piping exterior to the vessel, suchdistributor means permitting the resin to substantially occupy theinterior volume of the exchange vessel when the assembly is operated fordemineralization of the influent fluid flow; an auxiliary vesseloperative in association with the exchange vessel for receiving apredetermined portion of the ion exchange resin from the exchange vesselwhen the assembly is operated to backwash the resin; means fortransferring ion exchange resin between the exchange vessel and theauxiliary vessel; and the distributor means comprising a spiderdistributor having a main conduit, a first set of laterally disposedconduits in fluid communication with the main conduit and with theinterior of the exchange vessel; a second set of laterally disposedconduits in fluid communication with the interior of the exchangevessel, and means responsive to a control signal supplied thereto forselectively establishing fluid communication between the second set oflaterally disposed conduits and the main conduit.
 2. The ion exchangevessel assembly of claim 1 further including resin retaining meansassociated with the first set of laterally disposed conduits forpreventing resin from flowing from the interior of the exchange vesselinto the first set of laterally disposed conduits.
 3. The ion exchangevessel assembly of claim 2 wherein the resin retaining means comprises awire wrapping of multiple, spaced turns at least partially enclosingsaid conduits.
 4. The ion exchange vessel assembly of claim 1 whereinthe distributor means further includes internal flow control means forproportioning flow between said first and second sets of laterallydisposed circuits.
 5. The ion exchange vessel assembly of claim 4wherein the flow control means comprises a cooperating pair of flowcontrol members each of which comprises an annular member having aplurality of passages for fluid flow therethrough, the passages in eachof the flow control members being alignable by opposed rotation of theflow control members relative to each other, whereby the effectiveoperative size provided by the relative alignment of the passages in theflow control members may be adjusted.
 6. The ion exchange vesselassembly of claim 1 wherein the means operable for selectivelyestablishing fluid communication between the second set of laterallydisposed conduits and the main conduit comprises a remotely actuablevalve disposed between the second set of laterally disposed conduits andthe main conduit.
 7. The ion exchange vessel assembly of claim 6 whereinthe valve comprises a diaphragm valve.
 8. The ion exchange vesselassembly of claim 7 wherein the distributor means further includes achamber in fluid communication with the second set of laterally disposedconduits, the diaphragm valve being disposed in the path of fluid flowbetween said chamber and the main conduit.
 9. The ion exchange vesselassembly of claim 8 wherein one of the annular flow control members hasa first, closed end and an opposing, flanged end, said closed endconstituting a diaphragm stop member for the diaphragm valve.
 10. Theion exchange vessel assembly of claim 9 further including means foractuating the diaphragm of the diaphragm valve, said actuating meansincluding a fluid pressure source external to the ion exchange vessel.11. The ion exchange vessel assembly of claim 10 wherein the means foractuating the valve diaphragm further comprises a multi-state valvehaving at least three ports;a control tube operatively interconnecting afirst port of the multi-state valve with the diaphragm valve; a secondport of the multi-state valve being open to provide a vent; and a thirdport of the multi-state valve being connected to the fluid pressuresource, whereby when the multi-state valve is in a first state, thefirst port of the multi-state valve is connected to the third portthereof, thereby supplying pressure to the diaphragm valve from thepressure source, via the control tube, to close the valve diaphragm, andwhen the multi-state valve is in the second state, the first portthereof is connected to the second port thereof, thereby permittingpressure to be vented from the diaphragm valve via the control tube andthe second port, so that the diaphragm valve may open.
 12. The ionexchange vessel assembly of claim 11 wherein the multi-state valve isactuable in response to a control signal provided thereto to select oneof the first or second states thereof.
 13. The ion exchange vesselassembly of claim 12 wherein the multi-state valve is a three-waysolenoid valve.
 14. The ion exchange vessel assembly of claim 1 whereineach of the laterally disposed conduits comprises a tube having a boreextending longitudinally therethrough, from the end of the tubecommunicable with the main conduit through a substantial portion of thelength of the tube, and a plurality of radially directed bores extendingbetween the central bore and the exterior surface of the tube, so thatsuch radially directed bores provide passages permitting fluid flowbetween the interior of the exchange vessel and the central bores of thelaterally disposed conduits.
 15. The improvement of claim 1 wherein themeans for transferring resin includes means for removing ion exchangeresin from the exchange vessel at a predetermined level and means forreturning the resin to the exchange vessel at the same level.
 16. In afixed-bed ion exchange demineralizer system of the type having an ionexchange vessel containing a primary bed of ion exchange resin disposedtherein and upper and lower distributors for providing fluidcommunication between the interior of the vessel and a valve nest andpiping for controlling fluid flow to and from the vessel, theimprovement comprising the upper distributor comprising:a main conduit;two sets of laterally disposed conduits; the first set of laterallydisposed conduits being in fluid communication with the main conduit andwith the interior of the exchange vessel; the second set of laterallydisposed conduits being in fluid communication with the interior of theexchange vessel; means for selectively establishing fluid communicationbetween the main conduit and the second set of laterally disposedconduits responsive to a control signal; and means for retaining theresin in the exchange vessel and preventing the resin from flowing fromthe interior of the exchange vessel into the first set of laterallydisposed conduits.
 17. The apparatus of claim 16 wherein the laterallydisposed conduits of one of said first or second sets are of lesserlongitudinal extent than the other of said first or second sets, tooccupy lesser radial extent in the exchange vessel.
 18. The apparatus ofclaim 17 wherein the set of laterally disposed conduits of lesserlongitudinal extent is disposed uppermost within the top head of theexchange vessel.
 19. The apparatus of claim 18 wherein the lengths ofthe conduits of both said first and second sets of laterally disposedconduits are substantially less than the shell radius of the exchangevessel.
 20. The apparatus of claim 19 wherein the placement of thedistributor in the top head of the exchange vessel forms a concentratedhydraulic source within the confines of the top head volume.
 21. Theapparatus of claim 19 wherein the placement of the distributor withinthe top head of the exchange vessel forms a concentrated hydraulic sinkwithin the confines of the top head volume of the exchange vessel. 22.The apparatus of claim 21 wherein the placement of the distributor alsoforms a concentrated hydraulic source within the confines of the tophead volume.
 23. The apparatus of claims 20, 21 or 22 wherein thedistributor further provides a completely formed, full flowing hydraulicsource, to bring the influent fluid flow into contact with all portionsof the resin bed.